I have a 1980 D50. I recently swapped the 2.6L g54b motor into it. It has a weber carb, electric fuel pump, balance shaft delete, and jet valve delete. Aside from that, the it is stock. It ran for several months after the swap, but now dies whenever I slow down. It does not matter if I am in gear or neutral, it will die anyways. It runs perfectly fine otherwise. Giving it a little gas while braking keeps it alive. I've redone spark plugs and wires, redone the entire fuel system, and swapped out the brake booster but I cannot seem to fix the problem. Any advice?